I'm new to all of this 'turbo' information. I'm currently looking at a 2003.5 mazdaspeed protege 2.0L with turbo. The owner has installed a custom header, hard pipe kit for the intercooler, and a Greddy Type S bov. The stock on the turbo is 6lbs and he is going to give me a boost controller. How much boost could i notch onto this thing without risk of blowing the engine? would i need a gauge also? The car is on sale for 4 grand. is this a good buy if the condition is 'good'? it includes over 1000 dollars in audio with gps/nav.

 

The motor itself can take plenty of boost.. I have heard of mazda guys pushing as much as 25psi. The issue is if you have all the support mods to do so safely without hurting the motor. The other side of it is, is if the turbo is up to the task. I don't know if it would be out of it's efficiency range at that kind of power level. After all if it is all done by those pressures then you'll just be blowing hot air.

I don't know enough about mazdas to answer all your question as precisely as I would like. I hope this helps somewhat though.